Sealed contact relays are well-known in the electrical arts and have long found extensive application in electrical systems for performing a wide range of switching functions. These relays typically take the form of a pair of reed springs of a magnetically responsive and electrically conductive material suspended at their terminal ends by the envelope of a nonconductive material, usually glass, in which they are sealed. At their other ends the springs overlap and are spaced apart to present a contact gap. A winding encircling the envelope is energizable to generate a magnetic field to create a flux through the reed springs for urging their overlapping ends each toward the other to make electrical contact and thereby to control the electrical circuit in which the relay may be connected.
Although the familiar glass encapsulated reed spring relay has in the past served reliably and well, factors attending its fabrication and employment have prompted continuing efforts to achieve a simpler and sturdier relay construction. These factors include, for example, the realization of a gas-tight bond (if hermetically sealed) between the glass envelope and the retained metal contact springs and the accurate adjustment of the contact gap between the spring ends. The fragility of the bond also demands considerable care in the handling of the relay during installation and maintenance. As a result, a number of alternate reed spring relay structures have been proposed directed to the foregoing and other problems. In one prior art relay arrangement, for example, disclosed by the present inventor in U.S. Pat. No. 3,633,136, issued Jan. 4, 1972, the relay envelope comprises an insulating circular tube open at each end in which opposite ends the reed contact springs are inserted. The spring members are each mounted in a circular plug or cap which is inserted in, or fitted over, the open ends of the tube when the spring members have been fully inserted within the tube in an overlapping relationship.
A tube and end plug reed spring relay arrangement is also disclosed in the patent of W. M. Turner, U.S. Pat. No. 3,270,161, issued Aug. 30, 1966. In these and other broadly similar prior art approaches to relay assembly simplification, the problem of reed spring alignment and contact gap adjustment remains. Circular spring retaining means particularly, for example, may contribute to the difficulty of flat spring alignment contact gap accuracy. Unless the circular retaining means at opposite ends of the enclosing tube are fitted in precise radial alignment, deviation from the parallel of the planes of the overlapping flat springs results. Even a slight misfitting of the circular retaining means at the tube ends may also result in a significant variation from the optimum contact gap spacing. It is thus the problem of simplifying the construction and assembly of a reed spring relay while at the same time ensuring the precision of the relationship of the operating elements that the relay structure of this invention is chiefly directed.